U.S. patent number 11,352,279 [Application Number 16/957,107] was granted by the patent office on 2022-06-07 for rural landscape-type nitrogen and phosphorus ecological interception ditch system and farmland drainage nitrogen and phosphorus interception method using the same.
This patent grant is currently assigned to ZHEJIANG UNIVERSITY. The grantee listed for this patent is ZHEJIANG UNIVERSITY. Invention is credited to Shuang He, Junwei Jin, Fayong Li, Xinqiang Liang, Feng Liu, Ziyi Zhao.
United States Patent |
11,352,279 |
Liang , et al. |
June 7, 2022 |
Rural landscape-type nitrogen and phosphorus ecological
interception ditch system and farmland drainage nitrogen and
phosphorus interception method using the same
Abstract
A rural landscape-type nitrogen and phosphorus ecological
interception ditch system and a farmland drainage nitrogen and
phosphorus interception method using the system are provided. The
system includes a sediment buffer zone, an ecological ditch unit,
an interception-conversion pool and a field ridge hedge fence; the
sediment buffer zone, the ecological ditch unit, and the
interception-conversion pool are sequentially arranged in a
continuous ditch along a direction of a water flow; and the field
ridge hedge fence is arranged on field ridges on one side or both
sides of the ditch. The present disclosure can, on the basis of not
affecting normal production functions of a farmland, further exert
an ecological role of the farmland, and use the farmland as an
assimilation sink for environmental nitrogen and phosphorus, so as
to optimize drainage water quality and improve a farmland
ecological environment.
Inventors: |
Liang; Xinqiang (Hangzhou,
CN), Zhao; Ziyi (Hangzhou, CN), He;
Shuang (Hangzhou, CN), Liu; Feng (Hangzhou,
CN), Li; Fayong (Hangzhou, CN), Jin;
Junwei (Hangzhou, CN) |
Applicant: |
Name |
City |
State |
Country |
Type |
ZHEJIANG UNIVERSITY |
Hangzhou |
N/A |
CN |
|
|
Assignee: |
ZHEJIANG UNIVERSITY (Hangzhou,
CN)
|
Family
ID: |
65868733 |
Appl.
No.: |
16/957,107 |
Filed: |
September 18, 2019 |
PCT
Filed: |
September 18, 2019 |
PCT No.: |
PCT/CN2019/106536 |
371(c)(1),(2),(4) Date: |
June 23, 2020 |
PCT
Pub. No.: |
WO2020/114039 |
PCT
Pub. Date: |
June 11, 2020 |
Prior Publication Data
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|
|
|
Document
Identifier |
Publication Date |
|
US 20210387881 A1 |
Dec 16, 2021 |
|
Foreign Application Priority Data
|
|
|
|
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Dec 4, 2018 [CN] |
|
|
201811468836.9 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C02F
3/308 (20130101); C02F 3/305 (20130101); E02B
5/08 (20130101); C02F 1/283 (20130101); C02F
3/327 (20130101); C02F 3/303 (20130101); C02F
2307/00 (20130101); C02F 1/281 (20130101); C02F
2103/001 (20130101); C02F 2101/16 (20130101); C02F
3/302 (20130101); E02B 13/00 (20130101); C02F
3/32 (20130101); C02F 2101/105 (20130101) |
Current International
Class: |
C02F
3/30 (20060101); C02F 1/28 (20060101); E02B
5/08 (20060101); C02F 3/32 (20060101) |
Field of
Search: |
;210/601,602,615,616,617,747.2,747.3,150,151,170.03,259,903,906 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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203451288 |
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Feb 2014 |
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CN |
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206128023 |
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Apr 2017 |
|
CN |
|
106745692 |
|
May 2017 |
|
CN |
|
107512828 |
|
Dec 2017 |
|
CN |
|
109553191 |
|
Apr 2019 |
|
CN |
|
209276229 |
|
Aug 2019 |
|
CN |
|
20120041623 |
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May 2012 |
|
KR |
|
Other References
International Search Report (PCT/CN2019/106536); dated Dec. 12,
2019. cited by applicant.
|
Primary Examiner: Prince; Fred
Attorney, Agent or Firm: W&G Law Group
Claims
What is claimed is:
1. A rural landscape-type nitrogen and phosphorus ecological
interception ditch system, comprising a sediment buffer zone, an
ecological ditch unit, an interception-conversion pool and a field
ridge hedge fence, wherein the sediment buffer zone, the ecological
ditch unit, and the interception-conversion pool are sequentially
arranged in a continuous ditch along a direction of a water flow;
and the field ridge hedge fence is provided on field ridges along
one or both sides of the ditch; wherein a downward slope is
provided at a front end of the sediment buffer zone along a water
inflow direction, to form a water-fall zone, and an end of the
water-fall zone is connected to a ditch bottom of the ditch; a
buffer flow regulating wall perpendicular to the direction of the
water flow is provided downstream of the water-fall zone; and the
buffer flow regulating wall spans a cross section of the entire
ditch, a plurality of through-flow holes is arranged in the buffer
flow regulating wall, and a distribution density of the
through-flow holes decreases from top to bottom; wherein the
ecological ditch unit comprises an embedded
nitrification-denitrification-dephosphorization complete treatment
device and an aquatic plant community unit; the embedded
nitrification-denitrification-dephosphorization complete treatment
device is embedded in the ditch, for removing nitrogen and
phosphorus from farmland drainage; the aquatic plant community unit
is provided in the ditch downstream of the embedded
nitrification-denitrification-dephosphorization complete treatment
device, a slope-protection support is fixed on a side wall of a
ditch section where the aquatic plant community unit is located,
and support grids are densely arranged on the slope-protection
support, for planting emerging plants and submerged plants; wherein
the interception-conversion pool is provided in the embedded ditch,
and has a bottom that is lower than the ditch bottom, and a water
inlet and a water outlet that are flush with the ditch bottom; an
interior of the interception-conversion pool is divided into a
catchment area, an adsorption-interception area, and a water
storage and drainage area sequentially along the direction of the
water flow, a carbon-based filler wall that spans a cross section
of a pool body is provided in the adsorption-interception area, and
the catchment area--and the water storage and drainage area are
separated by the carbon-based filler wall so as not to be directly
communicated with each other; a shell of the carbon-based filler
wall adopts a porous frame, the porous frame has a hollow interior
and a water-permeable outer wall, and in an inner cavity thereof, a
water-inflow surface, a water-outflow surface and a bottom are
respectively laid with a sponge layer; a cavity between the sponge
layers is filled with two layers of different fillers, of which a
lower part is a percolation layer and an upper part is a
carbon-based adsorption filler layer; and wherein the field ridge
hedge fence is provided on the field ridges along one or both sides
of the ditch and a bottom thereof is a pebble zone laid on surfaces
of the field ridges, and emerging plants and/or wetland trees and
shrubs are planted on the pebble zone.
2. The rural landscape-type nitrogen and phosphorus ecological
interception ditch system according to claim 1, wherein the
embedded nitrification-denitrification-dephosphorization complete
treatment device has a bottom that is lower than the ditch bottom
of the ditch, a water inlet and a water outlet that are flush with
the ditch bottom, and a ""-shaped water-fall structure formed at a
position of the water inlet; a first baffle plate, a second baffle
plate, a third baffle plate, and a fourth baffle plate are provided
in a tank body of the treatment device, plate surfaces of the four
baffle plates are all perpendicular to the direction of the water
flow, a flow channel is kept between each baffle plate and a side
wall of the device, the flow channels between two adjacent baffle
plates and side walls of the device are located on different sides
of the device, and an interior of the treatment device forms a
""-shaped water flow channel under flow guidance of the four baffle
plates; the flow channels at sides of the first baffle plate, the
second baffle plate, the third baffle plate, and the fourth baffle
plate are provided with a plant growth bag module, an
iron-manganese composite oxide film module, a denitrification
module, and a phosphorus adsorbing medium module, respectively; the
plant growth bag module is composed of ecological concrete and
gravel disposed in an ecological bag, and holes for planting
emerging plants are provided in a bag body thereof; the
iron-manganese composite oxide film module is composed of
multi-faceted hollow spheres and gravel disposed in an ecological
bag, the multi-faceted hollow spheres being attached with
iron-manganese oxide films; the denitrification module is composed
of multi-faceted hollow spheres and gravel disposed in an
ecological bag, the multi-faceted hollow spheres being attached or
filled with a denitrification substrate; and the phosphorus
adsorbing medium module is composed of multi-faceted hollow spheres
and gravel disposed in an ecological bag, the multi-faceted hollow
spheres being attached or filled with a phosphorus adsorbing
medium.
3. The rural landscape-type nitrogen and phosphorus ecological
interception ditch system according to claim 1, further comprising
a tractor-ploughing road, wherein the tractor-ploughing road is
laid along one or both sides of the rural landscape-type nitrogen
and phosphorus ecological interception ditch system; and landscape
plants are planted along the tractor-ploughing road.
4. The rural landscape-type nitrogen and phosphorus ecological
interception ditch system according to claim 1, wherein a slope of
the water-fall zone has a gradient of 1:1-1:2.
5. The rural landscape-type nitrogen and phosphorus ecological
interception ditch system according to claim 1, wherein the buffer
flow regulating wall has a thickness of 20-30 cm, a height of
two-thirds of a height of the ditch, and a width same as that of
the ditch.
6. The rural landscape-type nitrogen and phosphorus ecological
interception ditch system according to claim 1, wherein the
slope-protection support is weaved with wicker or crop straw, and
side lengths of the support grids are 20-30 cm.
7. The rural landscape-type nitrogen and phosphorus ecological
interception ditch system according to claim 1, wherein a pool
volume of the interception-conversion pool is 1.5-3 m.sup.3, and
edges and the bottom of the pool are solidified with cement.
8. The rural landscape-type nitrogen and phosphorus ecological
interception ditch system according to claim 1, wherein the
carbon-based filler wall has a thickness of 40-60 cm, a top higher
than a top of the ditch, and a width same as that of the ditch; the
carbon-based adsorption filler layer is composed of rice husk
charcoal having a particle size of 3-5 mm and/or bamboo charcoal
having a particle size of 5-10 mm; and the percolation layer is
graded gravel having a particle size of 3-5 mm.
9. The rural landscape-type nitrogen and phosphorus ecological
interception ditch system according to claim 1, wherein the pebble
zone has a width of 0.3-0.5 m, is laid with pebbles having a
particle size of 3-10 cm, and maintains a gradient of 3-10%, and
the gradient is inclined to one side of the ditch.
10. A farmland drainage nitrogen and phosphorus interception method
using the rural landscape-type nitrogen and phosphorus ecological
interception ditch system according to claim 3, the farmland
drainage nitrogen and phosphorus interception method comprising the
following steps: 1) inputting farmland drainage that has been
converged and collected through drainage ditches into the nitrogen
and phosphorus interception system from the sediment buffer zone;
2) causing a water flow to pass through the water-fall zone, and
dissipating kinetic energy generated by falling of the farmland
drainage by using an increase of a water depth and blocking of the
buffer flow regulating wall, so that a flow velocity of the water
flow slows down and sediments settle; 3) causing the water flow to
continuously flow and enter the embedded
nitrification-denitrification-dephosphorization complete treatment
device, and performing falling water aeration at the water inlet of
the embedded nitrification-denitrification-dephosphorization
complete treatment device by using a high-low elevation drop while
further dissipating the energy; passing the farmland drainage
through the plant growth bag module after the falling water
aeration, and absorbing, by emerging plants, organic substances and
nutrient salts in the water as nutrients; concurrently,
transferring and releasing, by plant root systems, oxygen to make a
surrounding microenvironment sequentially aerobic, hypoxic, and
anaerobic, and intercepting and removing a part of nitrogen and
phosphorus pollutants through a nitrification-denitrification
effect and an excessive accumulation effect of phosphorus by
microorganisms; after treatment with the plant growth bag module,
the farmland drainage entering the iron-manganese composite oxide
film module, to catalytically oxidize ammonia nitrogen in the water
using an oxidation performance and an adsorption capacity of the
iron-manganese composite oxide film, to achieve a removal effect;
subsequently oxidizing ammonia nitrogen that is not adsorbed to
nitrate and nitrite into the water; after treatment with the
iron-manganese composite oxide film module, the farmland drainage
entering the denitrification module to undergo denitrification
using denitrification bacteria communities enriched in the
denitrification module and using the nitrate and nitrite produced
previously as electron donors, to reduce nitrate nitrogen to
nitrogen gas; after passing through the denitrification module, the
farmland drainage passing through the phosphorus adsorbing medium
module to allow phosphate in the water body to be adsorbed and
removed; and after treatment with the phosphorus adsorbing medium
module, discharging the farmland drainage from the outlet of the
treatment device to allow the farmland drainage to continue to flow
along the ditch into the aquatic plant community unit; 4) when the
farmland drainage flows through the aquatic plant community unit,
slowing down water flow of the farmland drainage through blocking
and sticking effects of emerging plants and submerged plants that
are planted on the ditch bottom and ditch walls, such that
suspended particles in the water further carry particulate organic
pollutants to precipitate and condense on the aquatic plant
communities and sediments on the ditch bottom and side walls of the
ditch; and adsorbing and degrading, by microorganisms and aquatic
plants in the sediments and the water, nitrogen, phosphorus and
organic pollutants; 5) after passing through the aquatic plant
community unit, the farmland drainage entering the catchment area
of the interception-conversion pool and performing adsorption and
sedimentation through the carbon-based filler wall; the farmland
drainage contacting the carbon-based adsorption filler layer during
flowing, so that nitrogen, phosphorus and organic substances in the
water body are adsorbed by the carbon-based adsorption filler and
then transformed and removed through metabolism of epiphytic
microorganisms in the filler; the farmland drainage at the
carbon-based adsorption filler layer flowing downwards along the
carbon-based filler wall to form a vertical flow and entering the
water storage and drainage area through the percolation layer; and
filtering and absorbing pollutants again when the farmland drainage
passes through the percolation layer; and 6) after treatment with
the interception-conversion pool, wastewater continuing to flow
along the ditch, to enter other water environments.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This is the United States national phase of International Patent
Application No. PCT/CN2019/106536, filed on Sep. 18, 2019, which
claims priority of Chinese patent application No. 2018114688369,
filed on Dec. 4, 2018, the entire contents of Which are
incorporated herein by their references.
TECHNICAL FIELD
The present disclosure relates to a rural landscape-type nitrogen
and phosphorus ecological interception ditch system and a farmland
drainage nitrogen and phosphorus interception method using the
system, and belongs to the technical fields of agricultural
non-point source pollution control and water environment
treatment.
BACKGROUND
Ecological ditch technology is similar to the artificial wetland
wastewater treatment technology that is widely used currently, and
nitrogen and phosphorus nutrients in farmland drainage in the
ditches are intercepted in many forms such as adsorption,
absorption, precipitation, filtration and microbial degradation
under a combined action of aquatic plants in the ditches and
microorganisms in sediments of the ditches. Roots of the aquatic
plants can directly absorb ammonia nitrogen, nitrate nitrogen and
phosphate in the farmland drainage and promote their exchanges at
an interface by breaking an interface balance, thereby accelerating
a speed of pollutants entering the sediments and enhancing their
interception capacity.
At present, China has a large number of newly constructed and
reconstructed ecological ditches, and these ecological ditches play
a significant role in non-point source sewage interception
treatment, but there are also problems that cannot be ignored:
1) an ordinary ecological ditch has a not-high removal efficiency
on the nitrogen and phosphorus pollutants, and it mainly depends on
emerging plants in the ditch and microbial communities in the
sediments to adsorb and absorb the nitrogen and phosphorus
pollutants. Biodiversity is single, ecosystem stability is
inadequate and it is susceptible to external influences. Due to
limitation of a plant amount, a contact area, a reaction efficiency
and a residence time, a removal rate of the nitrogen and phosphorus
is generally maintained at about 70%, and a treatment efficiency
will decrease after adsorption saturation of the system;
2) the pollutants adsorbed and absorbed in the ordinary ecological
ditch is not effectively handled, and when a rainstorm or flood
arrives, the pollutants will be reversely released into a water
body and the farmland in a form of leaching or dissimilation,
thereby causing secondary pollution.
3) the ordinary ecological ditch fails to take
"field-ridge-ditch-pool-road" as a unified whole, ecological
functions of the farmland have not been effectively developed, and
it does not meet construction requirements of beautiful countryside
and green ecological corridors.
SUMMARY
In view of the shortcomings that ecosystem functions of an existing
farmland are insufficient and interception and purification
capabilities of a ditch are weak, an object of the present
disclosure is to provide, on the basis of not affecting normal
production functions of the farmland and in order to further exert
its ecological role, a "field-ridge-ditch-pool-road" compound rural
landscape-type ecological ditch nitrogen and phosphorus
interception technology.
A specific technical solution adopted in the present disclosure is
as follows:
a rural landscape-type nitrogen and phosphorus ecological
interception ditch system includes a sediment buffer zone, an
ecological ditch unit, an interception-conversion pool and a field
ridge hedge fence; the sediment buffer zone, the ecological ditch
unit, and the interception-conversion pool are sequentially
arranged in a continuous ditch along a direction of a water flow;
and the field ridge hedge fence is provided on field ridges along
one or both sides of the ditch;
a downward slope is provided at a front end of the sediment buffer
zone along a water inflow direction, to form a water-fall zone, and
an end of the water-fall zone is connected to a ditch bottom of the
ditch; a buffer flow regulating wall perpendicular to the direction
of the water flow is provided downstream of the water-fall zone;
and the buffer flow regulating wall spans a cross section of the
entire ditch, a plurality of through-flow holes is arranged in the
buffer flow regulating wall, and a distribution density of the
through-flow holes gradually decreases from top to bottom;
the ecological ditch unit includes an embedded
nitrification-denitrification-dephosphorization complete treatment
device and an aquatic plant community unit; the embedded
nitrification-denitrification-dephosphorization complete treatment
device is embedded in the ditch, for removing nitrogen and
phosphorus from farmland drainage; the aquatic plant community unit
is provided in the ditch downstream of the embedded
nitrification-denitrification-dephosphorization complete treatment
device, a slope-protection support is fixed on a side wall of a
ditch section where the aquatic plant community unit is located,
and support grids are densely arranged on the slope-protection
support, for planting emerging plants and submerged plants;
the interception-conversion pool is disposed and embedded in the
ditch, and has a bottom that is lower than the ditch bottom, and a
water inlet and a water outlet that are flush with the ditch
bottom; an interior of the interception-conversion pool is divided
into a catchment area, an adsorption-interception area, and a water
storage and drainage area sequentially along the direction of the
water flow, a carbon-based filler wall that spans a cross section
of a pool body is provided in the adsorption-interception area, and
the catchment area and the water storage and drainage area are
separated by the carbon-based filler wall so as not to be directly
communicated with each other; a shell of the carbon-based filler
wall adopts a porous frame, the porous frame has a hollow interior
and a water-permeable outer wall, and in an inner cavity thereof, a
water-inflow surface, a water-outflow surface and a bottom are
respectively laid with a sponge layer; a cavity between the sponge
layers is filled with two layers of different fillers, of which a
lower part is a percolation layer and an upper part is a
carbon-based adsorption filler layer; and
the field ridge hedge fence is provided on field ridges along one
or both sides of the ditch and a bottom thereof is a pebble zone
laid on surfaces of the field ridges, and emerging plants and/or
wetland trees and shrubs are planted on the pebble zone.
Preferably, the embedded
nitrification-denitrification-dephosphorization complete treatment
device has a bottom that is lower than the ditch bottom of the
ditch, a water inlet and a water outlet that are flush with the
ditch bottom, and a ""-shaped water-fall structure at a position of
the water inlet; a first baffle plate, a second baffle plate, a
third baffle plate, a fourth baffle plate are provided in a tank
body of the treatment device, plate surfaces of the four baffle
plates are all perpendicular to the direction of the water flow, a
flow channel is kept between each baffle plate and a side wall of
the device, the flow channels between two adjacent baffle plates
and side walls of the device are located on different sides of the
device, and an interior of the treatment device forms a ""-shaped
water flow channel under flow guidance of the four baffle plates;
the flow channels at sides of the first baffle plate, the second
baffle plate, the third baffle plate, and the fourth baffle plate
are provided with a plant growth bag module, an iron-manganese
composite oxide film module, a denitrification module, and a
phosphorus adsorbing medium module, respectively; the plant growth
bag module is composed of ecological concrete and gravel disposed
in an ecological bag, and holes for planting emerging plants are
provided in a bag body thereof; the iron-manganese composite oxide
film module is composed of multi-faceted hollow spheres and gravel
disposed in an ecological bag, and the multi-faceted hollow spheres
are attached with iron-manganese oxide films; the denitrification
module is composed of multi-faceted hollow spheres and gravel
disposed in an ecological bag, the multi-faceted hollow spheres
being attached or filled with a denitrification substrate; and the
phosphorus adsorbing medium module is composed of multi-faceted
hollow spheres and gravel disposed in an ecological bag, the
multi-faceted hollow spheres being attached or filled with a
phosphorus adsorbing medium.
Preferably, a tractor-ploughing road is further included, and the
tractor-ploughing road is laid along one or both sides of the rural
landscape-type nitrogen and phosphorus ecological interception
ditch system; and landscape plants are planted along the
tractor-ploughing road.
Preferably, a slope of the water-fall zone has a gradient of
1:1-1:2.
Preferably, the buffer flow regulating wall has a thickness of
20-30 cm, a height of two-thirds of a height of the ditch, and a
width same as that of the ditch.
Preferably, the slope-protection support is weaved with wicker or
crop straw, and side lengths of the support grids are 20-30 cm.
Preferably, a pool volume of the interception-conversion pool is
1.5-3 m.sup.3, and edges and the bottom of the pool are solidified
with cement.
Preferably, the carbon-based filler wall has a thickness of 40-60
cm, a top higher than a top of the ditch, and a width same as that
of the ditch; the carbon-based adsorption filler layer is composed
of rice husk charcoal having a particle size of 3-5 mm and/or
bamboo charcoal having a particle size of 5-10 mm; and the
percolation layer is graded gravel having a particle size of 3-5
mm.
Preferably, the pebble zone has a width of 0.3-0.5 m, is laid with
pebbles having a particle size of 3-10 cm, and maintains a gradient
of 3-10%, and the gradient is inclined to one side of the
ditch.
Another object of the present disclosure is to provide a farmland
drainage nitrogen and phosphorus interception method using the
rural landscape-type nitrogen and phosphorus ecological
interception ditch system, and the method includes the following
steps:
1) inputting farmland drainage that has been converged and
collected through drainage ditches into the nitrogen and phosphorus
interception system from the sediment buffer zone;
2) cuasing a water flow to pass through the water-fall zone, and
dissipating kinetic energy generated by falling of the farmland
drainage flow using an increase of a water depth and blocking of
the buffer flow regulating wall, so that a flow velocity of the
water flow slows down and sediments gradually settle;
3) causing the water flow to continuously flow and enter the
embedded nitrification-denitrification-dephosphorization complete
treatment device, and performing falling water aeration at the
water inlet of the embedded
nitrification-denitrification-dephosphorization complete treatment
device by using a high-low elevation drop while further dissipating
the energy; passing the farmland drainage through the plant growth
bag module after the falling water aeration, and absorbing, by
emerging plants, organic substances and nutrient salts in the water
as nutrients; concurrently, transferring and releasing, by plant
root systems, oxygen to make a surrounding microenvironment
sequentially aerobic, hypoxic, and anaerobic, and intercepting and
removing a part of nitrogen and phosphorus pollutants through a
nitrification-denitrification effect and an excessive accumulation
effect of phosphorus by microorganisms; after treatment with the
plant growth bag module, the farmland drainage entering the
iron-manganese composite oxide film module, to catalytically
oxidize ammonia nitrogen in the water using an oxidation
performance and an adsorption capacity of the iron-manganese
composite oxide film, to achieve a removal effect; subsequently
oxidizing ammonia nitrogen that is not adsorbed to nitrate and
nitrite into the water; after treatment with the iron-manganese
composite oxide film module, the farmland drainage entering the
denitrification module to undergo denitrification using
denitrification bacteria communities enriched in the
denitrification module and using the nitrate and nitrite produced
previously as electron donors, to reduce nitrate nitrogen to
nitrogen gas; after passing through the denitrification module, the
farmland drainage passing through the phosphorus adsorbing medium
module to allow phosphate in the water body to be adsorbed and
removed; and after treatment with the phosphorus adsorbing medium
module, discharging the farmland drainage from the outlet of the
treatment device to allow the farmland drainage to continue to flow
along the ditch into the aquatic plant community unit;
4) when the farmland drainage flows through the aquatic plant
community unit, slowing down water flow of the farmland drainage
through blocking and sticking effects of emerging plants and
submerged plants that are planted on the ditch bottom and ditch
walls, such that suspended particles in the water further carry
particulate organic pollutants to precipitate and condense on the
aquatic plant communities and sediments on the ditch bottom and
side walls of the ditch; and adsorbing and degrading, by
microorganisms and aquatic plants in the sediments and the water,
nitrogen, phosphorus and organic pollutants;
5) after passing through the aquatic plant community unit, the
farmland drainage entering the catchment area of the
interception-conversion pool and performing adsorption and
sedimentation through the carbon-based filler wall; the farmland
drainage contacting the carbon-based adsorption filler layer during
flowing, so that nitrogen, phosphorus and organic substances in the
water body are adsorbed by the carbon-based adsorption filler and
then transformed and removed through metabolism of epiphytic
microorganisms in the filler; the farmland drainage at the
carbon-based adsorption filler layer flowing downwards along the
carbon-based filler wall to form a vertical flow and entering the
water storage and drainage area through the percolation layer; and
filtering and absorbing pollutants again when the farmland drainage
passes through the percolation layer; and
6) after treatment with the interception-conversion pool,
wastewater continuing to flow along the ditch, to enter other water
environments.
The present disclosure can, on the basis of not affecting the
normal production functions of the farmland, further exert its
ecological role, and use the farmland as an assimilation sink for
environmental nitrogen and phosphorus, so as to achieve a purpose
of optimizing drainage water quality and improving ecological
environment of the farmland. In order to solve the problems that
the ecological functions of the existing farmland are insufficient
and the interception and purification capabilities of the ditch are
weak, the present disclosure optimizes a role of the
"field-ridge-ditch-pool-road" in the entire composite system,
enriches farmland biodiversity, increases buffering, beautifying
and economic functions of the field ridge, improves an environment
landscape effect and a pollution self-purification ability of the
water body, and caters to needs of beautiful rural construction,
striving to build a farmland green ecological corridor and promote
green development of the agriculture.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a cross-sectional diagram of an ecological ditch
according to the present disclosure;
FIG. 2 is a partially enlarged schematic diagram of a buffer flow
regulating wall in FIG. 1;
FIG. 3 is a schematic diagram of a slope-protection support in FIG.
1;
FIG. 4 is a partially enlarged schematic diagram of the
slope-protection support in FIG. 3;
FIG. 5 is a cross-sectional diagram of an interception-conversion
pool in FIG. 1;
FIG. 6 is a top diagram of an interception-conversion pool in FIG.
1;
FIG. 7 is a longitudinal sectional diagram of a carbon-based filler
wall in FIG. 5;
FIG. 8 is a cross-sectional diagram of a field ridge hedge
fence;
FIG. 9 is a cross-sectional diagram of an embedded
nitrification-denitrification-dephosphorization complete treatment
device; and
FIG. 10 is a top diagram of an embedded
nitrification-denitrification-dephosphorization complete treatment
device;
Reference numerals of the present disclosure are as follows:
TABLE-US-00001 1--water-fall area 2--ditch bottom 3--buffer flow
regulating wall 4--through-flow hole 5--embedded nitrification-
6--slope-protection support denitrification-dephosphorization
complete treatment device 7--support grid 8--emerging plant
9--submerged plant 10--interception-conversion pool 11--catchment
area 12--adsorption-interception area 13--water storage and
drainage area 14--carbon-based filler wall 15--porous plastic frame
16--sponge 17--carbon-based adsorption filler layer 18--percolation
layer 19--pebble zone 20--wetland trees and shrubs
DESCRIPTION OF EMBODIMENTS
The present disclosure is further interpreted and described below
with reference to the drawings and specific embodiments. The
technical features of various embodiments of the present disclosure
can be combined correspondingly under the premise that there is no
confliction between each other.
In a preferred embodiment of the present disclosure, a rural
landscape-type nitrogen and phosphorus ecological interception
ditch system is as shown in FIG. 1. Basic functional units of the
rural landscape-type nitrogen and phosphorus ecological
interception ditch system can be divided into a sediment buffer
zone, an ecological ditch unit, an interception-conversion pool and
a field ridge hedge fence. The sediment buffer zone, the ecological
ditch unit, and the interception-conversion pool are sequentially
arranged in a continuous ditch along a direction of a water flow,
while the field ridge hedge fence is provided on field ridges along
one or both sides of the ditch. The respective functional units can
be constructed by excavating an existing farmland drainage ditch,
or corresponding structures are formed through complete
re-excavation, but the essence thereof is an ecological ditch
having ditch nitrogen and phosphorus capacities. The respective
functional units in this system have different functions, and a
structure and a role of each of the functional units are described
in detail below.
The sediment buffer zone is arranged upstream of the ditch and used
to reduce a speed of the water flow entering the system, so that
the sediment is deposited, preventing subsequent functional units
from being blocked. A downward slope is provided at a front end of
the sediment buffer zone along a water inflow direction to form a
water-fall zone 1. A gradient of the water-fall zone is set 1:1-1:2
according to an actual size of the ditch and water flow conditions.
A rear end of the water-fall zone 1 is connected to a ditch bottom
2 of the ditch and is in a same plane as the ditch bottom. A buffer
flow regulating wall 3 perpendicular to the direction of the water
flow is provided downstream of the water-fall zone 1, and the
buffer flow regulating wall 3 spans a cross section of the entire
ditch. After the water flow passes through the water-fall zone,
since a water depth increases and a flow velocity decreases,
buffering is achieved, so that it is more conducive to sediment
settlement; the buffer flow regulating wall 3 that is provided
behind the water-fall zone 1 and is perpendicular to the reaction
of the water flow has a thickness of 20-30 cm, a height of
two-thirds of an actual height of the ditch, and a width same as an
actual width of the ditch. As shown in FIG. 2, through-flow holes 4
are evenly arranged in the buffer flow regulating wall 3, and the
through-flow holes 4 are arranged in a configuration in which a
distribution density gradually decreases from top to bottom, so as
to achieve a better effect of blocking the sediment to ensure
cleanliness of tailwater. The buffer flow regulating wall is used
to collide with a shortly accelerated water flow formed by flow
falling in the water-fall zone to consume kinetic energy generated
by the flow falling, and to slow down the water flow passing
through the buffer flow regulating wall and uniform the flow
velocity, such that the water flow has deep and slow
characteristics under a combined effect of the water-fall zone 1
and the buffer flow regulating wall 3, thereby greatly improving
the sedimentation effect of the sediment. The sediment accumulated
by the sedimentation can be regularly dredged and removed according
to the actual situations, to prevent fluidity of the water flow in
the ditch from being blocked.
The ecological ditch unit includes an embedded
nitrification-denitrification-dephosphorization complete treatment
device 5 and an aquatic plant community unit. The embedded
nitrification-denitrification-dephosphorization complete treatment
device 5 is located upstream, and the aquatic plant community unit
is located downstream.
The embedded nitrification-denitrification-dephosphorization
complete treatment device 5 is embedded in the ditch, for removing
nitrogen and phosphorus from farmland drainage. Its specific
structure is shown in FIG. 9 and FIG. 10, and the embedded
nitrification-denitrification-dephosphorization complete treatment
device 5 is a cube recess formed by further excavating downwards on
the basis of the ditch, so a bottom of the device is lower than the
ditch bottom 2 of the ditch, and a water inlet and a water outlet
of the device are flush with the ditch bottom 2, forming a
""-shaped water-fall structure at a position of the water inlet. A
position of the water-fall structure may be configured in a manner
that the water falls vertically or with a slope having a certain
angle of inclination. The gradient of the bottom of the entire
device along the direction of the water flow, that is, the
inclination slope is 0.3-0.5%, and this gradient enables the water
flow to automatically flow under the gravity without additional
energy consumption.
A baffle plate A5-7, a baffle plate B5-8, a baffle plate C5-9, and
a baffle plate D5-10 are provided in a tank body of the treatment
device, and a length of each baffle plate is smaller than a width
of a cross section of the recess, so that a flow channel is kept
between each baffle plate and a side wall of the device. Adjacent
baffle plates are disposed on different side walls of the recess,
and the flow channels between two adjacent baffle plates and the
side walls of the device are located on two sides of the device,
respectively. Therefore, it can be seen from the drawing that a
middle-section recess of the treatment device forms an ""-shaped
water flow channel under guidance of the four baffle plates. The
flow channels at sides of the baffle plate A5-7, the baffle plate
B5-8, the baffle plate C5-9, and the baffle plate D5-10 are
provided with a plant growth bag module 5-2, an iron-manganese
composite oxide film module 5-3, a denitrification module 5-4, and
a phosphorus adsorbing medium module 5-5, respectively. Each of the
modules is wrapped by an ecological bag, to prevent it from being
washed away by the water flow. The ecological bags are bags made of
water-permeable materials with meshes, such as gunny-bags,
geotextiles, etc., and different functional module materials are
loaded into the bags to perform different functions. Specific
arrangements of the different modules are described in detail below
one by one.
The plant growth bag module 5-2 consists of ecological concrete,
gravel and emerging landscape plants placed in the ecological bag.
The gravel is of a certain type, and is disposed in the ecological
bag to play a role of stabilizing a position of the bag body to
prevent displacement with the water flow, and the gravel in other
bags described below also play a similar role. The emerging
landscape plants 5-6 are planted on the ecological concrete, and
tops thereof protrude out of the bag body through openings in the
ecological bag, beyond a water level 5-1, and can be exposed to
sunlight. It is recommended that yellow iris or canna or the like
is used as the emerging landscape plants, so that plant stems can
be used to adsorb and absorb pollutants in water, and meanwhile a
good ornamental performance is provided. The paddy field drainage
carrying sediments firstly passes through the nitrogen and
phosphorus rapid coupling plant growth bag containing the emerging
plants, and organic substances and N, P and other elements in the
water can be intercepted and used by the plant as nutrient
substrates, so that a load of a subsequent processing module is
reduced. Transferring and releasing of oxygen by plant root systems
causes the surrounding microenvironment to sequentially be aerobic,
hypoxic and anaerobic, to achieve a purpose and effect of
intercepting and removing some pollutants through the
nitrification-denitrification and an excessive accumulation of the
phosphorus by microorganisms. The iron-manganese composite oxide
film module 5-3 is composed of multiple-faceted hollow spheres
disposed in an ecological bag, and gravel can be placed in the
ecological bag as required. An iron-manganese composite oxide film
is attached to or filled in the multiple-faceted hollow spheres.
The iron-manganese composite oxide film can be prepared and coated
on the multiple-faceted hollow spheres by any method in the related
art and can also be compounded on the surface of the
multiple-faceted hollow spheres by using commercially available
materials. The iron-manganese composite oxide film has an amorphous
structure, with main constituent elements being iron, manganese,
calcium, oxygen and so on, and since it has a relatively large
specific surface area and hydroxyl functional groups, it has a good
oxidation performance and an adsorption capacity, and thus can have
effective catalytic oxidization of ammonia nitrogen in water to
achieve the removal effect. However, due to the limited oxidation
and adsorption capacity of the iron-manganese oxide film, the
ammonia nitrogen that is not adsorbed is easily oxidized into
nitrate and nitrite, which enter into the water and then are
further converted into three-cause substances that can cause
cancer, malformation and mutations and are harmful to human health,
so further treatment is needed subsequently. The denitrification
module 5-4 is composed of multi-faceted hollow spheres disposed in
an ecological bag, and gravel can also be placed in the ecological
bag as required. Denitrification substrate is attached to the
multi-faceted hollow spheres. The denitrification substrate is a
layer of biofilm or sediments with denitrification bacterium. The
multi-faceted hollow spheres may be placed in acclimatized
sediments having the denitrification bacterium for a period of time
and is taken out and put into the ecological bag after the film is
formed. In this embodiment, a part of the denitrification sediments
and the multi-faceted hollow spheres are directly mixed and filled
in the bag, and then the sediments can be attached and filled in
void spaces of the spheres, so that during the treatment process,
the surfaces of the multi-faceted hollow spheres will be gradually
formed with films. In other embodiments, multi-faceted hollow
spheres that have been formed with films in the denitrification
zone in a reactor or a sewage treatment facility can also be
directly taken and filled into the bag. The phosphorus adsorbing
medium module 5-5 is composed of multi-faceted hollow spheres
disposed in an ecological bag, and gravel can be placed in the
ecological bag as required. A phosphorus adsorbing medium is
attached to or filled in the multi-faceted hollow spheres, and the
phosphorus adsorbing medium is mainly composed of calcite and
phosphate modified products thereof, and removes the phosphate by
adsorption. The calcite is a carbonate mineral of which crystals
are of a trigonal crystal system, low in cost and easy to obtain,
and the product after it adsorbs phosphate can again be used for
removing phosphate in water. The calcite can be ground into powder,
then kneaded into a spherical shape and filled into cavities of
multi-faceted hollow spheres, or it is ground into powder and then
sprayed onto surfaces of the multi-faceted hollow spheres.
In the device of this embodiment, the ecological bag used by the
respective module has a volume of 0.003-0.005 m.sup.3 and has a
height that is not beyond the ditch bottom 2. The heights of the
tops of the four baffle plates are flush with the ditch bottom 2,
and a plate thickness is 1-2 cm. Surfaces of the bottom of the
device and the recess wall of the device in the middle-section of
the treatment device are rough, to facilitate formation of the film
and strengthen the treatment of drainage.
The aquatic plant community unit is provided in the ditch
downstream of the embedded
nitrification-denitrification-dephosphorization complete treatment
device 5, and this unit is reconstructed based on the ditch itself.
A slope-protection support 6 is fixed on a side wall of a ditch
section where the aquatic plant community unit is located, and
support grids 7 are densely arranged on the slope-protection
support 6. Emerging plants 8 and submerged plants 9 may be planted
in the support grids and the ditch bottom to increase the diversity
of animals and plants of the ditch, in order to make the unit form
a complete ecological circle of "aquatic plants-micro aquatic
animals-microbial community". When the paddy field water flows
through the aquatic plant community unit, the water flow is slow
and uniform due to blocking and sticking effects of the emerging
plants and the submerged plants at the ditch bottom. Through the
sedimentation, suspended particles SS in the paddy field water
further carry particulate organic pollutants to settle and condense
on the aquatic plant communities and sediments at the ditch bottom
and the side walls. Active bacteria micelles and aquatic
microorganisms in the sediments and the water adsorb organic
pollutants through a relatively large specific surface area and
absorb, transform, and assimilate the organic pollutants into
biomass through metabolism in an aerobic environment, to complete
removal of biochemical oxygen demand BOD; whereas the aquatic
plants and rhizosphere biospheres that grow depending thereon
adsorb nitrogen-containing pollutants and some
phosphorus-containing pollutants in the water through root system
adsorption and an synergistic effect and transform them into
nitrogen gas and organic phosphorus through the nitrification
reaction, denitrification reaction, and phosphorus adsorption and
release reaction, to complete the removal.
In this embodiment, the slope-protection support is weaved by
wicker or crop straw, and a side length of the support grid is
20-30 cm.
Pollutants in the farmland drainage can be blocked and assimilated
in the plant ecosystem, but a process of sedimentation and plant
absorption is relatively slow. Thus, when a treatment flow rate is
relatively large, water discharge requirements cannot be met, so it
is necessary to be assisted with other treatment processes to
ensure the water discharge effect. In this embodiment, it is
achieved by providing the interception-conversion pool 10 at the
end of the ditch. The interception-conversion pool 10 is disposed
and embedded in the ditch, the interception-conversion pool is
connected to the ditch, the bottom of the interception-conversion
pool 10 is lower than the ditch bottom 2, and the water inlet and
the water outlet of the interception-conversion pool 10 are flush
with the ditch bottom 2. According to actual situations of the
ditch, a size of the pool volume of the interception-conversion
pool to 1.5-3 m.sup.3, a pool bottom is lower than the ditch
bottom, and edges and the bottom of the pool are solidified with
cement. As shown in FIG. 5 and FIG. 6, the pool is divided into
three systems, that is, it is sequentially divided into a catchment
area 11, an adsorption-interception area 12, and a water storage
and drainage area 13 along the direction of the water flow. A
carbon-based filler wall 14 that spans a cross section of the pool
body is provided in the adsorption-interception area 12, and the
catchment area 11 and the water storage and drainage area 13 are
separated by the carbon-based filler wall 14 so as not to be
directly communicated. The interception-conversion pool 10 adsorbs
and assimilates nitrogen and phosphorus in runoff of the paddy
field water through the adsorption effect and the
nitrogen-phosphorus conversion effect, thereby achieving the
purpose of process interception and loss reduction of the nitrogen
and phosphorus.
The carbon-based filler wall has a length of 50 cm and a width same
as that of the ditch, and it is slightly higher than the ditch top,
so that the paddy field water can fully contact the carbon-based
filler wall, to adsorb and settle the pollutants in the water. For
the carbon-based filler wall, a movable porous frame 15 made of
relatively hard plastic is used as a shell, to facilitate
periodical removal and replacement. An interior of the porous frame
15 is hollow, and openings are formed in an outer wall of the
porous frame 15 to form a water-permeable structure. The internal
structure of the frame is shown in FIG. 7, and in its inner cavity,
a water-inflow surface, a water-outflow surface and a bottom are
respectively laid with a sponge layer 16 of 2 to 3 cm. If
necessary, all surfaces of the inner cavity may be covered by a
sponge layer to prevent loss of relatively small filling particles.
A cavity between the sponge layers 16 is filled with two layers of
different fillers, of which a lower part is a percolation layer 18
and an upper part is a carbon-based adsorption filler layer 17. The
percolation layer 18 may be formed by stacking of watertight
particulate filter materials, for percolating drainage. The
carbon-based adsorption filler layer 17 uses a carbon-based
adsorption material, such as conventional activated carbon. In this
embodiment, the percolation layer 18 is filled with graded gravel
with a particle size of 3-5 mm, and a filling height is one quarter
of the height of the carbon-based filler wall. The graded gravel
may be preferably composed of a mixture of ceramsite, sandstones
and cobblestones with a filling volume ratio of 1:1:1, and has a
better percolation and pollutant-discharge effect. The carbon-based
adsorption filler layer 17 uses rice husk charcoal having a
particle size of 3-5 mm or bamboo charcoal having a particle size
of 5-10 mm, and a filling height is three-quarters of the height of
the carbon-based filler wall. The two kinds of charcoals can be
used individually or in combination, and preferably, the rice husk
charcoal and bamboo charcoal are mixed and filled with a volume
ratio of 1:2. Of course, specific fillers in the two filler layers
can also be adjusted as needed. The percolation layer can cause the
suspended pollutants in the water body to be settled and adsorbed,
the carbon-based adsorption filler layer can effectively absorb
eutrophic pollutants in the water body such as nitrogen and
phosphorus, and the nitrogen and phosphorus left on the
carbon-based filler wall are transformed by the microorganisms,
thereby improving the water treatment effect of the farmland
drainage.
Since the percolation layer 18 is located at the bottom in the
carbon-based filler wall 14, the farmland drainage will present a
horizontal and vertical composite subsurface flow pattern in the
adsorption-interception area. A water flow at the top of the
carbon-based filler wall 14 will flow downwards along the wall body
with the pollutants being adsorbed by the carbon-based filler
during the flowing process, and after entering the percolation
layer 18, begin to enter the subsequent water storage and drainage
area 13 in a form of a horizontal flow. As for the pollutant in the
farmland drainage, the organic pollutant particles having different
particle sizes are first intercepted by the blocking and screening
effect of the filter materials, then adsorbed by the filter
material and epiphytic microorganisms in the filter material, and
transformed and removed by microbial metabolism. Since the
saturated carbon-based material has adsorbed nutrients such as
nitrogen and phosphorus, and has enhanced fertility, it can
continue to be used for agriculture as fertilizer of non-edible
plants or soil conditioner to achieve a purpose of resource
utilization.
A field ridge hedge fence is provided on the field ridges along one
or both sides of the ditch where the nitrogen and phosphorus
interception system is located, and its bottom is a pebble zone 19
laid on a surface of the field ridge. The emerging plants 8 and
wetland trees and shrubs 20 are planted on the pebble zone 19. The
field ridge hedge fence are provided according to the conditions of
the ditch, and it is recommended that pebble zones, emerging plants
and wetland trees and shrubs are provided on the field ridges along
one or both sides of a ditch that has a relatively large scale, and
only pebble zones and emerging plants are laid on the field ridges
along one or both sides of a ditch that has a relatively small
scale. A width of the pebble zone is set 0.3-0.5 m according to an
actual width of the field ridge of the ditch, and the pebble zone
is laid with pebbles having a particle size of 3-10 cm, and
maintains a slope of 3-10%. The slope is inclined to one side of
the ditch, and the pebble zone in the hedge fence are densely
planted with plants outwardly as required. The field ridge hedge
fence can be used as an ecological protection slope that protects
the ditch, and when the ditch is full of water or a flood arrives,
the field ridge hedge fence can form a wetland buffer zone together
with the ditch, thereby stabilizing soil, controlling a flood, and
preventing sewage from outflowing to cause secondary pollution;
when a rainstorm occurs, the field ridge hedge fence can not only
prevent, through the blocking effect of the pebble zone and the
roots, stems and leaves of the plants, the rainstorm from carrying
foreign matters to the ditch to lead to blocking or pollution, but
also evenly buffer a water volume of the rainstorm, to protect the
ditch system. A companion system composed of the field ridge hedge
fence and the ecological ditch units can form an ecological
community of a relatively high level, which strengthens the paddy
field water treatment and also forms good water-front ecological
landscapes, thereby meeting construction needs of beautiful
ecological fields and farmland green ecological corridors.
After the farmland drainage passes through the respective units
above, the sediments therein are effectively settled, whereas
organic substances, such as the nitrogen and phosphorus, which are
likely to cause eutrophication, are also efficiently removed, and
the drainage can continue to enter other water environments along
the ditch.
Without doubt, in another embodiment, tractor-ploughing roads that
serve as roadways can also be constructed on both sides of the
ecological ditch. Ecological corridors are constructed on both
sides or one side of the tractor-ploughing road, and plant types,
population structures, plant spacings, zone widths, and zone
spacing parameters of the ecological corridor are determined
according to different regions: a spacing between trees is
generally 1.5-2 m, a shrub is planted between two trees, and a
grass zone is planted under the shrubs, a width of the grass zone
is 0.5-1 m, specifically determined by the width of the
tractor-ploughing road; trees, shrubs, and herbaceous plants are
planted in combination to achieve biodiversity while achieving
nitrogen and phosphorus enrichment and plant landscape economic
effects.
In the present disclosure, the plants planted in the entire system
can be determined as needed. The emerging plants include, but are
not limited to, reeds, cattails, acorns calamus, and canna; the
submerged plants include, but are not limited to, Vallisneria
asiatica, hornwort, myriophyllum, and najas minor; the herbaceous
plants include, but are not limited to, reeds, cattails, acorns
calamus, and canna; the wetland trees and shrubs include, but are
not limited to, cattail, hibiscus, Yucca gloriosa, and wisteria.
When selecting species, a ratio of indigenous plants is increased
as many as possible and introduction of the wetland plants to
disrupt existing local ecological balance is avoided, and the
planting ratio should be determined according to local
conditions.
Plants in the ecological ditch units and the field ridges need to
be harvested every autumn, and the plants are treated by anaerobic
composting, poultry feeding, and economic plant deep processing and
the like, to prevent secondary pollution caused by release of the
nitrogen and phosphorus pollutants and to achieve environmental and
economic benefits, to give back to the society.
Based on the nitrogen and phosphorus interception system, the
farmland drainage can be intercepted and transformed. Moreover, in
the nitrogen and phosphorus interception system, the number of each
different unit may be set one as shown in FIG. 1, or more than one
at different positions along a flow path of the farmland drainage
ditch. A method for intercepting and transforming the farmland
drainage based on the nitrogen and phosphorus interception system
is described in detail below, and includes the following steps:
1) after the farmland drainage is converged and collected through a
ditch, it is input to the nitrogen and phosphorus interception
system from the sediment buffer zone;
2) a water flow is caused to pass through the water-fall zone, and
kinetic energy generated by falling of the farmland drainage is
dissipated due to increase of a water depth and blocking of the
buffering flow regulating wall 3, so that a flow velocity of the
water flow slows down and sediments gradually settle;
3) the water flow is caused to continuously flow and enter the
embedded nitrification-denitrification-dephosphorization complete
treatment device 5, and perform falling water aeration at the water
inlet of the complete treatment device 5 by using a high-low
elevation drop while further dissipating the energy; the farmland
drainage passes through the plant growth bag module 5-2 after the
falling wateraeration and organic substances and nutrient salts in
the water are absorbed by emerging plants as nutrients;
concurrently, plant root systems transfer and release oxygen to
make a surrounding microenvironment sequentially be aerobic,
hypoxic, and anaerobic, and a part of nitrogen and phosphorus
pollutants is intercepted and removed through a
nitrification-denitrification effect and an excessive accumulation
effect of the phosphorus by microorganisms; after treatment with
the plant growth bag module 5-2, the farmland drainage enters the
iron-manganese composite oxide film module 5-3, and ammonia
nitrogen in the water are catalytically oxidized using an oxidation
performance and an adsorption capacity of the iron-manganese
composite oxide film, to achieve a removal effect; ammonia nitrogen
that is not adsorbed is subsequently oxidized to nitrate and
nitrite into the water; after treatment with the iron-manganese
composite oxide film module 5-3, the farmland drainage enters a
denitrification module 5-4, and nitrate nitrogen is reduced to
nitrogen gas through denitrification by using denitrification
bacteria communities enriched in the denitrification moduleand
using the nitrate and nitrite produced previously as electron
donors; after passing through the denitrification module 5-4, the
farmland drainage passes through a phosphorus adsorbing medium
module 5-5 to allow phosphate in the water body to be adsorbed and
removed; after the treatment with the phosphorus adsorbing medium
module 5-5, the farmland drainage is discharged from the outlet of
the treatment device and continues to flow along the ditch into the
aquatic plant community unit;
4) when the farmland drainage flows through the aquatic plant
community unit, flowing of the water flow is slowed down by a
blocking and sticking effects of emerging plants and submerged
plants that are planted on the ditch bottom and ditch walls, such
that suspended particles in the water further carry particulate
organic pollutants to precipitate and condense on the aquatic plant
communities and sediments on the ditch bottom and side walls of the
ditch; and microorganisms and aquatic plants in the sediments and
the water adsorb and degrade nitrogen, phosphorus and organic
pollutants;
5) after passing through the aquatic plant community unit, the
farmland drainage enters the catchment area 11 of the
interception-conversion pool 10 and performs adsorption and
sedimentation through the carbon-based filler wall 14; the farmland
drainage contacts the carbon-based adsorption filler layer 17
during flowing, so that nitrogen, phosphorus and organic substances
in the water body are adsorbed by the carbon-based adsorption
filler and then transformed and removed through metabolism by
epiphytic microorganisms in the filler; the farmland drainage at
the carbon-based adsorption filler layer 17 flows downwards along
the carbon-based filler wall 14 to form a vertical flow and enters
the water storage and drainage area 13 through the percolation
layer 18; and when the farmland drainage passes through the
percolation layer 18, pollutants are filtered and absorbed
again;
6) after treatment with the interception-conversion pool 10,
wastewater continues to flow along the ditch, to enter other water
environments for irrigation or to be discharged into rivers and
lakes.
The embodiments described above are only preferred solutions of the
present disclosure, but are not intended to limit the present
disclosure. Those of ordinary skill in the related art may make
various changes and modifications without departing from the spirit
and scope of the present disclosure. Therefore, any technical
solution obtained by adopting an equivalent replacement or
equivalent transformation falls within the protection scope of the
present disclosure.
* * * * *